On Mon, Dec 02, 2013 at 08:01:57AM -0600, Darren Addy wrote: > Larry, > I'm very impressed by what you got, particularly considering your Thank you Darren.
> challenge in finding dark skies. Where were these taken? If you look at the photo on flickr, and click on where it says Rincon california, it should call up a map. It was taken with the GPS afterall. The short answer is that it is the north west corner of the UCSC campus, on Empire Grade, abouta mile south of Smith Grade. > The beauty of the O-GPS1 is that you don't have to futz with polar > alignment. The downside is that you do have to futz with "precise > calibration", which would often confirm working before I had even > completed three axis OR fail to confirm when I had done everything > (carefully) correctly. Then all of the sudden it might work. I've only found that to be a minor annoyance. I can't help but wonder if the OGPS 1 can do real time correction, so that if it were on a polar mount that wasn't perfectly alligned, would it make it work better? Or would it assume that it is a solid tripod and you'd get reverse correction? > > Regarding the ballhead, I think that with a decent ballhead you can do > widefield work, but it helps to have a red dot finder or laser pointer > in the hotshoe to help you aim. As you know, it is best if your > subject is in the center of the field since that is were the best lens > performance will be - corners being where coma and changes in flatness > of field might show up. There is that, but I honestly couldn't see anything to precisely aim by. I used zoom lenses at the wide end, and hoped to get the galaxy someplace in the exposure, to dial in on. > > Regarding the lens selection, nothing torture-tests a lens like > astrophotography. Astrophotography will reveal CA and coma like > nothing else. Not all lenses will be suited to astrophotography, given > just those two criteria. You are also NEVER going to get the lenses > best image wide open, regardless of maximum aperture. You should > always try (or compare) stopping down 1 stop from maximum. Since that > is the case, I think that you should give more weight to the aperture > and less to the focal length, particularly when you are starting out. > f/6.3 obviously requires a much longer exposure time than f4 for > example. That longer exposure time is going to make more evident > problems in your tracking (or influences from other things like > vibrations in the ground, sagging of your ballhead, etc. The longer > the exposure time the smaller percentage of your subs will be > acceptable for stacking. Plus, it is in stacking that you effectively > build up the integrated exposure. Finally, longer exposures in less > than dark-sky conditions are going to result in you recording the > background as less than black. Once that happens you aren't gaining > anything with a longer exposure because you have reached the contrast > limit. You don't HAVE to do it with single long exposures. That's for > the guys with the "real" equatorial set-ups. That being said, I was > able to get decent exposures of up to 45 seconds with a K135mm f2.5 > stopped down to f4. These were 30 seconds at 200mm, so that is about the same rule of 6,000. I think we want to keep the multiplier down to about 3,000, maybe 2,000. > > Even in the film days, a 200mm f/4 lens was the one most often used > for widefield astrophotography. That equates to a 135mm on APS-C. Your > 200mm shots look very very good. With a DA* 200mm f2.8 you might even > have the option of using it wide open AND you can get the benefits of > the lens profile corrections. There's at least a thousand and one reasons that I'm using the 80-200 that I'm borrowing from John F rather than a DA* 200. The one being able to zoom out to help my aiming. > > Regarding DeepSkyStacker crashing, make sure you are using the latest > beta. For some reason if you Google DSS the page you get doesn't give > you access to the latest program. Check to see if you are using this > version: > http://deepskystacker.free.fr/download/DeepSkyStacker333beta51.rar No, I was using 3.32 stable. 3.33 beta worked fine. Thanks. It took some massaging it with lightroom to pull it out: http://www.flickr.com/photos/ellarsee/11174029125/ I also tried a couple of black and white conversions that I added to the end of the set.. I think that I would have had better luck earlier in the evening. By the time I ended, it was getting close to the horizon. > > -d > > On Sun, Dec 1, 2013 at 11:53 PM, Larry Colen <[email protected]> wrote: > > On Sun, Dec 01, 2013 at 10:36:13PM -0600, Christine Aguila wrote: > >> Very nice, work, Larry! Excellent. Cheers, Christine > > > > Thanks Christine. > > > > I spent most of the day trying to get stacking programs to work and > > get a cleaner version. I finally got an image out of nebulosity, but > > it looked worse than what I got from a single frame. > > > > Meanwhile I loaded Deep Sky Stacker on the Windows laptop I use > > for work, and it would just choke and crash. > > > > At some point, I'll give it another try, and I learned some important > > things. Like, with astrotracer, it seems like focal length time > > seconds seems to need to be below 3,000 (200mm * 15 Sec) maybe a bit > > less. > > > > That's five times better than the 600 rule. > > > > > >> > >> Sent from my iPad > >> > >> > On Dec 1, 2013, at 6:06 AM, Larry Colen <[email protected]> wrote: > >> > > >> > > >> > http://www.fluidr.com/photos/ellarsee/sets/72157638239972733/ > >> > > >> > Even with the astrotracer 30 seconds at 500mm is too long. > >> > Now, I need to find stacking software for my mac. > >> > > >> > These were photographed on Empire grade at the gate for Grey Whale ranch, > >> > with my Pentax K-5 II, using my O-GPS 1 in astrotracer mode. > >> > Some were shot with John Francis' 80-200/2.8 and some with my bigma. > >> > > >> > I learned that using a ballhead sucks for astrophotography. It is > >> > impossible to make fine adjustments in just one axis. Hell, it is > >> > impossible to make accurate fine adjustments period. > >> > > >> > -- > >> > Larry Colen [email protected] > >> > http://red4est.com/lrc > >> > > >> > > >> > -- > >> > PDML Pentax-Discuss Mail List > >> > [email protected] > >> > http://pdml.net/mailman/listinfo/pdml_pdml.net > >> > to UNSUBSCRIBE from the PDML, please visit the link directly above and > >> > follow the directions. > >> > > >> > >> -- > >> PDML Pentax-Discuss Mail List > >> [email protected] > >> http://pdml.net/mailman/listinfo/pdml_pdml.net > >> to UNSUBSCRIBE from the PDML, please visit the link directly above and > >> follow the directions. > > > > -- > > Larry Colen [email protected] http://red4est.com/lrc > > > > > > -- > > PDML Pentax-Discuss Mail List > > [email protected] > > http://pdml.net/mailman/listinfo/pdml_pdml.net > > to UNSUBSCRIBE from the PDML, please visit the link directly above and > > follow the directions. > > > > -- > I don't have a problem with idiots. > I have a problem with the fact that they have an internet connection. > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- Larry Colen [email protected] http://red4est.com/lrc -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
